For only the third time history, a US president is going on trial in the Senate.
It’s all but certain that Donald Trump will be acquitted – his Republican party is in the majority in the Senate, and a two-thirds vote is required to convict him and remove him from office.
Before the trial begins in earnest, senators will need to agree the rules of the trial. Democrats would like to call witnesses and are not afraid of a longer process. The Republican Senate leader, Mitch McConnell has vowed to wrap it up as quickly as possible.